Washing composition



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Patented Jan. 29, 1952 WASHING COMPOSITION Vladimir Dvorkovitz and Thomas G. Hawlcy, Jr.,

Chicago, Ill., assignors to The Diversey Corporation, a corporation of Illinois I No Drawing. Application September 30, 1947, Serial No. 777,112

3 Claims. (Cl. 252-156) This invention relates to a composition that is particularly applicable for washing bottles and other forms of glassware and to the washingsolutions prepared from such compositions.

The industries that wash large quantities of bottles and other glassware, such as the dairy, brewery, and soft drink bottlers, have found it expedient to adopt a continuous process wherein the bottles are conveyed first through a tank or tanks containing a strongly alkaline solution and then through a. rinsing solution. The glassware is maintained in the alkaline solution until it has become cleaned. It has been found that when the glassware and those parts of the equipment adjacent the glassware pass through the alkaline solutions, they are coated with a film of alkali. When the alkali-coated objects are immersed in the rinse water. an immediateprecipitation occurs of the dissolved calcium and magnesium salts that are present in the rinse water. The precipitated solids form a hard scale on the glassware and particularly on the equipment. Because of the intimate contact of the film of alkali with the glassware and equipment, the precipitate appears to be more adherent and accounts for the scale type of deposition rather than the more desirable sludge or non-adherent precipitate. This scale continues to build up on the equipment until it is necessary that the scale be removed. This removal involves a considerable economic loss in time, labor and materials employed in the scale removal.

The problem of the scale formation has received considerable recognition and much effort has been spent to overcome it. For example, many complex alkali metal salts of phosphoric acid have the property of holding calcium and magnesium compounds in solution that are normally insoluble. Certain amino carboxylic acid derivatives have also been used for this purpose. It has been found, however, that none of these compounds work effectively in the presence of sodium hydroxide. Thus, a sufllcient quantity of sodium hexametaphosphate willslhold the hard water precipitates usually obtained by adding sodium carbonate or sodium orthophosphate to a hard water solution. However, long standing of the product or standing at less time at elevated temperatures causes hydrolysis of the resulting complex and causes precipitation of the calcium and magnesium compounds. This effect is even more pronounced if even small quantities of caustic alkalis are present.

The present invention is concerned with means for preventing the formation of this scale on glassware and on parts of the equipment used in washing the glassware that comes in contact with the washing and rinsing solutions. We have found that a composition comprising a water soluble alkali metal hydroxide such as sodium hydroxide or potassium hydroxide and an alkali metal salt of a hydroxy carboxylic acid having a total of at least three of the radicals: hydroxyl and carbo'xyl, will prevent or at least minimize the formation of an adherent hard water scale. The hydroxides of sodium and potassium are preferred because of their inexpensiveness and availability, but the hydroxides of other elements of the alkali metal group may be used if desired. One of the salts which has been found to be particularly effective is sodium gluconate. The alkali metal salts include those of gluconic acid, citric acid, tartaric acid, mucic acid, and malic acid as well as many others. The acids themselves may also be used.

The fact that these salts will not form precipitates in the presence of sodium hydroxide is surprising as it has been noted that precipitates will form when such alkalis as sodium carbonate, sodium orthophosphate, sodium silicate and the like are employed. with the salts in the absence of sodium hydroxide andthe like. These alkaline materials may be used, however, if they are used in combination with sodium hydroxide.

It has been found that even if some scale is formed on the equipment or is mechanically picked up by passage through a sludge, it is redissolved when it is repassed through the caustic soda-salt solution. v

The solution is quite stable and can be maintained at 150 F. for two weeks or more without any apparent decomposition or precipitation. The compositions that are employed in making the washing solutions preferably contain from 5 to 99% by weight of an alkaline material including an alkali metal hydroxide and from to 1% of the alkali metal salt of the hydroxy carboxylic acid. The major proportion of the alkaline material should be the hydroxide. An alkali stable wetting agent may also be used in preparing the solutions.

In testing the value of the invention, solutions were prepared employing a Chicago city water that had an approximate hardness of P. P. M., 3% by weight of sodium hydroxide and 0.2% of various sequestering or repressing agents. The solutions were formed and their appearance was noted. They were all heated until the water boiled and any difference in appearance was also noted. Some of the materials prevented meoccurred. In some cases this was due to the de- TABLE I 3% NaOH solution in Chicago tap water sequestering or Repressing Agent gggg gzg fi gf .2% Sodium gluconate .2% Glucose .2% Sorbitol .2% Sodium hexametaphosphatm .2% Tripolyphospliate .2% Sodium tetraphosphate .2% Tetrasodium pyrophosphete .2% Nullapon A .2% Saccharic acid- I .2% Mucic acid .2% Sodium carboxy methyl cellulose (med. yisc.)

.2% Malic acid If the 3% caustic soda solution were added to hard water containing as high as 3% of a complex phosphate such as sodium hexametaphosphate, a precipitate would form. It has been found that the effect of the salt of the hydroxy carboxylic acid is in the main independent of the concentration of the caustic soda. Thus. solutions of caustic soda as high as 30% can be used when only 0.2% of the salt is used. However, very minute quantities of caustic soda can allow the formation of a precipitate, and it has thus been found that the solution must have a pH higher than 12 for effective results.

The results shown in Table I show the difference between precipitation and the prevention of precipitation. The table does not, however, indicate where the amount of precipitate is reduced. It was discovered that some of the hydroxy carboxylic acids and their salts might permit the formation of a considerable amount of precipitate, but the amount of scale deposited on the glassware or equipment was reduced. This eflect in preventing scale as apart from preventing precipitation might be due to some effect which delays the precipitation and prevents its deposition on the glassware and equipment. All the hydroxy carboxylic acids and their salts appear to have at least this latter effect.

The caustic soda-salt combination also serves to prevent softening and subsequent scratching of the glassware. It has been found that the addition of such agents as trisodium phosphate, sodium carbonate, or the like, to sodium hydroxide solutions assist in the cleaning of glassware. However, these agents have a marked effect in that they serve as catalysts for the sodium hydroxide and cause it to soften andpartially dissolve the glass. easily marked by the machinery or by abrasion against other pieces of glass and soon receives an unsightly appearance. The use of the caustic soda-salt solutions as cleansing agents avoids this I softening and dissolving. Tests were made toprove this fact. Various solutions were prepared using 5% concentrations of sodium hydroxide. The materials used and the results'obtained are shown in the following table. In obtaining these results, the glass was held in contact with each solution for 72 hours at 145 F.

TABLE 11 Per Oglt losls in For clintfloss in weig 0 c our wclg t 0 green Composition milk bottle soft drink glass bottle glass 7 N CH Per cent Per cent 90 a 10% Sodium glucouate 100% NaOH .102 .002 NBOH 077 Um 5 0% Sodium Aluminate. 96.0% NaOH 067 4 0% NazHPO4 94.5% NaOH 5.0% Sodium gluconatev .054 .052 .5% N ullapon B 94.0% NaOi-i 4.0% Trisodium phosphate ll7 2.0% Sodium aluminate.

Another advantage to be obtained by the use of sodium-hydroxide-salt combination is that the solution serves as a better inhibitor of rust and corrosion of steel and iron than sodium hydroxide solutions alone. Still another advantage is that the solutions are relatively nonfoaming.

The following table lists, on a dry basis, some of the many possible-combinations that have been used successfully in cleaning operations and which because of the incorporation of a caustic soda-sodium gluconate combination do not give precipitation or reduce precipitation to a marked degree in hard water solutions.

TABLE III Components Components by Wgt.

Caustic soda 90 80 89. 5 85 81. 5 91 Sodium gluconate- 10 20 10.0 5 7. 5 5 'lrisodium phosphat 1.0 2 Sodium carbonate--- 10.0 Zinc oxide 2 Sodium salt of higher aikyl sulfates. 6

7 water scale, it has also been found that this com- Hence, the glass is more bination has been further improved by the provision of an alkali metal salt of an amino carboxylic acid derivative having the general formula orb-coon CHI-000E where R is a member of the class consisting of -c-cooH Hi0 on, R1 R1 H] H:

C El

CHrCO OH CHrC O OH CHaCOOH groups. The groups may contain substituents so long as the resulting compounds are still water soluble.

The combination of the above amino carboxylic acid derivatives together with, for example, sodium gluconate are eflective agents for repressing precipitates that would normally be formed if mixtures of caustic soda with other alkalis such as soda ash or the alkali metal salts of phospohric acid were added to hard water. It ha also been found that other combinations of alkali metal salts or'amino carboxylicacids and hydroxy carboxylic acids are eflective in preventing or diminishing the formation of precipitates when alkalis containing free caustic alkalis are added to hard water. Thus, the compounds obtained from the phenylene diamines by reaction with chloroacetic acid are effective in combination with, for example, sodium gluconate in preventing the precipitation of calcium and magnesium salts from hard water.

If 0.5% of an alkali metal salt oran amino polycarboxylic acid derivative is added to hard water of 150 P. P. M. hardness and then 5% of caustic soda added, an immediate gelatinous precipitate is formed which does not go into solution on raising the temperature above ordinary room temperature. If instead 01' using the to the hard water and then 5% o! caustic soda and 5% or sodium carbonate added, a clear solution results that stays clear even when heated to boiling and then permitted to stand overnight. similarly, the sodium carbonate may be substituted by trisodium phosphate and the resulting solution remains clear even when brought to the boiling point and permitted to stand overnight. The use of sodium gluconate only does not permit such high concentration of sodium carbonate or trisodium phosphate without the formation of a precipitate.

. Acids such as acetic acid or polyalcohols such as glycerine or sorbitol do not have this effect caustic soda, 5% of soda ash or 5% of trisodium phosphate is added, either no precipitate is formed or a light gelatinous precipitate is formed that dissolves on warming the solution. If a mixture of caustic soda with either soda ash or trisodium phosphate is added to the water containing the alkali metal salt 01' an amino polycarboxylic acid derivative, a precipitate is with the amino polycarboxylic acid salt. but hyd'roxy acids, for example, citric acid, maleic acid, tartaric acid, and mucicacid to prevent or reduce the formation of precipitates when used 7 in combination with the above-mentioned amino carboxylic acid derivatives. Thus, it 0.05% or the amino derivative and 0.25% o! mucic acid are added to Chicago tap water and 4.5% of caustic soda and 0.5% or trisodium phosphate are added, a clear solution results in the cold, but on warming a light gelatinous precipitate begins to separate at about 190 F. If the mucic acid is substituted by tartaric acid. the same results are obtained.

Furthermore, it 0.25% of sodium gluconate and 0.2% of the alkali metal salt of the amino carboxylic acid derived from the reaction of paraphenylene cliamine with chloroacetic acid are added to Chicago tap water and then a mixture 01' 2.5% caustic soda and 2.5% soda ash are added, the resulting solution is free from precipitates and can be brought to the boiling point and still remain clear.

Various other tests were peri'ormed. to show the effectiveness of the present invention in eliminating or reducing the precipitates formed when using caustic soda in hard water. These tests and their results are summarized in the following table:

TABLE IV Hydroxy Acid or Salt 7 AlkaliCombinsthereof (or other Amino carboxylic ggg g z tion a ent in cases Acid derivative w are) 15 NaOH G1 cerin .057 sodium eth lene rcci itate.

y m; imino diacgtate. p p 5% NaOH Bol'bitol .05% sodium ethylene Do.

7 N OH bis lmino diaeetste. 4.5 a

a p a MM ("assesses p 0s a 4.6% aOH 7 g ggg 193 2 35315333? pmipmte' 4.5%,, aOH..-

.57, Trisodium .5% 'Iartarlc acid Do. isg fiaor f' ;g g g {addresses B p p 05% N, N'N tetra precipitate. 4.5% NaOH..... methyl tetra air- .5% Trisodium boxylic acid deriv.

phosphate. of phenylene di- 05 13 i; NN' tctra clear a. 4.57 NaOH v .5% Trisodium }.5% sodium giuconate. igg g; hosphatc. p oip ylsnediaminc. 4.5% Na0H.----

.67 'lrisodium 5% sodium gluconate. precipitate.

phosphate. 7

formed regardless of the relative concentration so long as at least 5% of the total alkali is caustic alkali.

As an example or the efl'ectiveness or sodium gluconate or the like, it 0.5% of the amino compound and 0.5% or sodium gluconate are added when .5 gm. of the sodium salt of trimethyl amino a, a, a". tricarboxylic acid is added to 100. grams of Chicago tap water and then 5 rams of NaOH be added. a light gelatinous precipitate results. Itinstead or adding 5 ms. or NaOH.5gms.otsodaaahhadbecnadded the resultant solution would have been clear.

Now, if to this clear carbonate solution guns. of NaOH is added a precipitate results. Now, however, if .5 gm. of the sodium salt of trimethyl amino 9., a, a", tricarboxylic acid together with .5 gm. of sodium gluconate and then 5 gms. of NaOH and 5 gms. of NazCO;- are added, a clear solution results. This shows the eflect therefore of the use of a combination of hydroxy acid and amino carboxylic acid derivative in preventing precipitation.

As examples of the invention, an identical experiment was repeatedusing difierent solutions whereby a continuous steel chain of known weight was passed through a caustic solution and then through a rinse water of 1000 P. P. M. hardness and back through the caustic solution. This was repeated continuously for a period of eight hours when the chain was removed from the system, dried, and weighed and its appearance noted.

that such pH is obtained in the presence of sumcient water to give a pH reading.

Having described our invention as related to the embodiment described herein, it is our intention that the invention be not limited by any of the details of description unless otherwise specified, but rather be construed broadly within its spirit and scope as set out in the accompanying claims.

We claim:

1. A composition consisting essentially of a mixture of 1 to sodium gluconate and 99 to 80% alkaline material, with some of the alkaline material being sodium carbonate in an amount up to about 10% thereof and the remainder being sodium hydroxide.

2. A composition adapted for making a washing solution with water for washing glassware,

TABLE V Weight of 5% alkali solutions comprising: Appearance of Chain scale in grams Caustic Soda 1&2, Heavy white scale .2580 Caustic Soda v t g i-i }He3\ Y hue scale Jaus 1c 0 a gifig gogg y Whlte Scale 5409 s 10 Sodium Hcxametaphosphate. ,i whlm Scale 115 Soda }l-leavy white scale 150 Caustic Soda.: 3 l 1 1 (sl ghtlconate @2 22? }Bright nl v 0039 .nustic So a iodlilum 21%c0nate 5. 0 /2 }Bright, very slight scale.-." .0461 i u upon }Bright, very slight scale." 0458 Caustic Soda: .90 Sodium carboxymethyl cellulose i ery shght ggg g i g g' }Bright, very slight scale"--. 101 Caustic Soda: 20-4, 3-t5 dimethylene gluconic acid 907 ishght Scale 1373 aus 10 so a 0 3-6 D Glucosaccharolactone l0% }Shght some 1336 1 Slight increase.

The Nullapon '3 is ethylene bis imino diacetic acid, or a salt thereof; specifically, it is sodium ethylene bis imino diacetate.

The hydroxy carboxylic acids are known to give lactones when subjected to an intermolecular dehydration process. This dehydration is shown in the following equation:

Hydroxy acid Lactoue In an aqueous solution of the alkali, the lactone can hydrolyze to give the alkali salt of the hydroxy carboxylic acid. Thus, it is possible to use lactones in place of the acids or the salts and the the alkali on glassware, the gluconate being present in an amount up to about 10 parts by weight.

3. A composition adapted for making a washing solution with water for washing glassware, comprising about 90 parts by weight of sodium hydroxide and about 10 parts by weight of sodium gluconate.

05 Number VLADIMIR DVORKOVITZ. THOMAS G. HAWLEY, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date 729,600 Jones ...1 June 2, 1903 2,145,827 Chester Jan. 31, 1939 2,291,085 Lehmkuhl et a1. Ju1y 28, 1942 2,346,562 De Long Apr. 11, 1944 2,419,805 Wegst et al Apr. 29, 1947 FOREIGN PATENTS Number Country Date France 1 May 31. 1943 

1. A COMPOSITION CONSISTING ESSENTIALLY OF A MIXTURE OF 1 TO 20% SODIUM GLUCONATE AND 99 TO 80% ALKALINE MATERIAL, WITH SOME OF THE ALKALINE MATERIAL BEING SODIUM CARBONATE IN AN AMOUNT UP TO ABOUT 10% THEREOF AND THE REMAINDER BEING SODIUM HYDROXIDE. 